Compounds related to organic Dirac electron systems (ODES) using linear gold(I) complex anions

Area of Science:

• Materials Science
• Solid-State Physics
• Organic Electronics

Background:

• Organic Dirac electron systems (ODES) exhibit unique electronic properties.
• Different ODES types, such as α- and α'-type salts, lead to distinct material behaviors like zero-gap semiconductors and nodal-line semimetals.
• Understanding structure-property relationships in ODES is crucial for designing novel electronic materials.

Purpose of the Study:

• To synthesize and characterize Bis[bis(ethylenedithio)tetraselenafulvalene(0.5+)] dibromidoaurate(I) and its chloride analogue (BETS₂AuX₂, X = Cl, Br).
• To investigate the crystal and band structures of these novel BETS₂AuX₂ compounds.
• To elucidate the influence of structural features and electronic states on the resulting material properties.

Main Methods:

• Single-crystal X-ray diffraction for crystal structure determination.
• Band structure calculations using computational methods.
• Synthesis of BETS₂AuX₂ compounds.

Main Results:

• The synthesized BETS₂AuX₂ compounds possess crystal structures combining features of both α- and α'-type ODES.
• Band structure calculations indicate that BETS₂AuX₂ materials are close to zero-gap semiconductors.
• The α-type structural feature was identified as the dominant factor governing the band structures.

Conclusions:

• The crystal and band structures of BETS₂AuX₂ are primarily governed by the α-type structural arrangement, leading to near zero-gap semiconductor behavior.
• Differences in crystal structures between BETS₂IX₂ and BETS₂AuX₂ arise from the strength of BETS-anion interactions, not solely geometrical factors.
• Electronic states of constituents can significantly impact crystal and band structures in ODES, sometimes beyond expectations based on geometry alone.